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Black silicon photodetector breaks 100% efficiency limit



Black silicon photodetector breaks 100% efficiency limit

UV light causes electrons to multiply in nanostructures. Credit: Wisa Förbom

Aalto University researchers have developed a black silicon photodetector that has achieved over 1

30% efficiency. Thus, for the first time, a photovoltaic device has exceeded the 100% limit, which was previously considered as the theoretical maximum for external quantum efficiency.

“When we saw the results, we could hardly believe our eyes. We immediately wanted to verify the results with independent measurements,” says Prof. Hele Savin, head of the Electron Physics research group at Aalto University.

Independent measurements were performed by the German National Metrology Institute, Physikalisch-Technische Bundesanstalt (PTB), which is known to provide the most accurate and reliable measurement services in Europe.

Head of PTB Laboratory of Detector Radiometry, Dr. Lutz Werner comments, “After seeing the results, I immediately realized that this is a significant step forward – and at the same time, a very welcome step forward for metrologists dreaming of higher sensitivities.”

The secret of progress: unique nanostructure

The external quantum efficiency of a device is 100% when an incoming photon generates an electron in the external circuit. 130% efficiency means that an incoming photon generates approximately 1.3 electrons.

The researchers found that the origin of the extremely high external quantum efficiency lies in the charge-carrier multiplication process within silicon nanostructures driven by high-energy photons. The phenomenon has not been observed earlier in current devices as the presence of electrical and optical losses has reduced the number of electrons collected.

“We can assemble all multiplied cargo carriers without the need for special external bias as our nanostructured device is without recombination and loss of reflection,” explains Prof. Savin.

In practice, record efficiency means that the performance of any device that is using light detection can be drastically improved. Light detection is already widely used in our daily lives, for example, in cars, cell phones, smartwatches and medical devices.

“Our detectors are gaining a lot of traction at the moment, especially in biotechnology and industrial process monitoring,” says Dr. Mikko Juntunen, CEO of Aalto University spin-off company Elfys Inc. They are already producing record detectors for commercial use.

Results leading to record efficiency have been accepted for publication in Physical Review Letters in an article titled “Ultraviolet photodiodes with black silicon achieve external quantum efficiency over 130%”.


Efficient valves for electron rotation


More information:
Garin et al. Black silicon ultraviolet photodiodes achieve external quantum efficiency over 130%, Physical Review Letters (2020). revista.aps.org/prl/accepted/… 234ffbcb06f4a5ba1ac5, arxiv.org/abs/1907.13397

Provided by Aalto University



citation: Black silicon photodetector breaks 100% efficiency limit (2020, August 14) Retrieved August 14, 2020 from https://phys.org/news/2020-08-black-silicon-photodetector-efficient-limit.html

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